Masamune, also known as Goro Nyudo Masamune (Priest Goro Masamune), is widely recognized as Japan's greatest swordsmith. As no exact dates are known for Masamune's life, he has reached an almost legendary status. It is generally agreed that he made most of his swords in the late 13th and early 14th centuries, 1288-1328. He created swords, known as tachi in Japanese and daggers called tanto, in the Soshu tradition. He is believed to have lived and worked in the Sagami Province (Kamakura). Some old stories list his family name as Okazaki, but some experts believe this is a fabrication to enhance the standing of the Tokugawa family.

An award for swordsmiths exists called the Masamune prize which is awarded at the Japanese Sword Making Competition. Although not awarded every year it is presented to a swordsmith who has created an exceptional work. Masamune is believed to have worked in Sagami Province during the last part of the Kamakura-era (1185-1333), and it is thought that he was trained by swordsmiths from Bizen and Yamashiro provinces, such as Saburo Kunimune, Awataguchi Kunitsuna and Shintogo Kunimitsu.

Masamune is believed to have trained a great number of sword smiths, 15 are known, 10 of which are considered to be the Juttetsu or 'Ten Famous Students' or "10 Great Disciples of Masamune".